(1) You need to find a small nation with a poor and corrupt government. The less international support/allies they have, the better. The weaker the government's hold on power, and the smaller the military, the better. But you still need a place where you can safely live while you work on your nation; in the middle of a civil war is not a good idea, since your nation will likely end when your brain gets splattered in the line of fire, or when the rebels sack your little community for supplies and kill everyone.

(2) You need to get into this country. You can probably get in as a tourist, but obtaining a visa for some places can be difficult. You might have to cross the border illegally…

(3) You lay low for a couple decades. You need to spend this time making friends and supporters out of the locals in the area you want to be your nation. You need to stay below the existing regime's radar though, because if they hear about your attempts at sedition, you will find yourself the object of a manhunt. Then, you will have to stay a few steps ahead of the authorities…

(4) While building up such support, you need a continuous flow of supplies and the funds to purchase those supplies. You should make whatever you can with existing tools, but whatever your little separatist community cannot make, you need to import. If your operation is discovered, you might have to be nomadic, and you will have to smuggle all those supplies in.

(5) Your first objective should be self-sufficiency. That ALWAYS comes before sovereignty. If you are reliant on your neighboring macronation for vital supplies, they can just cut those supply lines and strangle your new nation into submission. You need a fully functional economy, with sufficient agriculture, industry, and the infrastructure to support both. These things should be your highest priority.

(6) Assuming things work out OK so far, you need an effective public relations arm to spread propaganda about your new nation. It has to be good enough to convince the locals to join your project, and it has to create worldwide sympathy and support for your new nation. Without that, you will just be an obscure nobody.

(7) You need to properly defend yourself, especially if the existing regime is corrupt and greedy. They will likely not allow you to peacefully secede, so be prepared to fight a full-scale war for your independence. "Si vis pacem, para bellum." = "If you want peace, prepare for war." Also, "Do not make yourself a mouse, or the cat will eat you." Both phrases ring very true for both micro- and macro-nations alike, and you will need to adopt these lessons into your society. The Gandhi technique will not work against a corrupt dictator, and it certainly will not work if your supporters number only a few thousand. You need many millions for that to work; otherwise, the powers that be will happily crush you.

(8) Now that you have the army, the industry, and the economy, you are a de facto macro-nation. Time to become fully independent. Send your declaration of independence, ask for a peaceful solution, prepare for imminent attack, and wait.
(9) If the regime attacks, your public relations arm needs to spin the news in such a way that it generates mass sympathy for your plight and that of the locals who support you. If the regime commits crimes against humanity and violates the Geneva convention (perhaps by executing prisoners), use that. Spin the regime you are fighting as a hopelessly corrupt tyrannical dictatorship who is committing genocide, and the democracies of the world will take notice. Aim for an audience in 1st-world nations, like America and the members of the EU. If you get enough support there, you could get some freedom fighters to join you.

(10) Employ said foreign freedom fighters in battle against the regime that opposes you. Unless you have technological and/or numeric superiority (which you probably do not), hold back most of your forces for homeland defense, and let the foreigners do most of the fighting. Whatever you do, do not make it obvious that you are doing this! Appear to have a very weak army (roughly 10% of your actual strength), and hide the rest of your forces. This will lull the enemy into a false sense of superiority, which will make him relax his guard, and the enemy will weaken (it is a tactic favored by the great Sun Tsu). Employ guerrilla tactics, and use asymmetrical warfare to wear the enemy down. Do not resort to terrorism, and conduct yourself in a manor superior to that of your enemy! This lets you take the moral high ground.

(11) As foreign freedom fighters get killed in this war, their families back home will stir up trouble, and demand that their nation's government do something to end the fighting. If you keep up with the public relations and manipulation, popular demand will force those larger nations to align themselves to your side by way of sympathy. Keep the PR campaign going, and eventually, you just might see some economic and/or military aid come your way from another macronation. The UN might deploy peacekeepers to protect your new nation, and/or they might levy sanctions against your enemy. If America decides to get involved, you definitely want them on your side, whether you like the American regime or not, you need to take advantage of any other nation's willingness to use its own soldiers to help you. (Why die when others are willing to do it for you?)

(12) Now that almost everybody is pissed at the regime for trying to suppress your new nation, the concept of their defeat in this war is very desirable. Now is the time to deploy the full force of your military. Storm the old nation's capitol, capture their leaders, and force the regime to sign a treaty legitimatizing your claim as a sovereign nation. Be kind though, and give them back any territory that you captured but did not originally want, and offer to set up trade and/or friendship treaties. Convince the defeated regime that they actually have a choice, and they will probably take you up on the friendship/non-aggression offer. That way, it looks like they are getting something in exchange for losing the territory that is now your nation.

(13) Congratulations. You are now on the map. Consolidate your national strength, and try to get some other macro-nations to trade and/or ally themselves with you. What you do from here, and the fate of your new nation, is all up to you.